Thread milling with single point tool question

[bbatarelo]

Hi all,

I have two single point thread milling tools ordered from Lakeshore Carbide and have tried thread milling cycle - internal. It worked, but clearance between tool shank and edge of the hole was so small that I thought the tool will break. Can someone explain me how Centroid knows the dimensions of the single point tool (radius)?
Also I was experimenting with different setting for Number of Passes field, but from what I could see that doesn't result in gradually going deeper and deeper on every pass. Rather on first pass tool plunges into the wall all the way and remaining passes are just like cleanup passes.
Am I doing something wrong? What is the correct setup/prerequisites for thread milling cycle?

Thank you,
Bruno

[suntravel]

Centroid uses the tool diameter in the Tool Setup to calculate the toolpath.

Second pass is only a spring pass.

If you want the first pass not on the full depth, use a second tool number for the same tool with a larger diameter in the settings.

Uwe

[bbatarelo]

Thank you! I kind of presumed that the answer would go in this or similar direction. In my industry (software engineering) this sort of solution would be considered "a hack" - seemingly not so much in CNC world

Best,
Bruno

[tblough]

In your industry, this would be considered a user workaround for the freeware version. You could of course pay $15K for the full version (Mastercam, SolidCAM), or go the subscription route (Fusion360) and pay through the nose forever.

Many thread mill companies also offer on-line or downloadable G-code generators:
https://sct-usa.com/thread-mill-code-generator/
https://www.guhring.com/Tech/threadmillgenerator
https://www.osg.co.jp/en/media_dl/thread_pro/

[cnc_smith]

The tooling company will give you the range for the threads per inch (pitch for metric) so the shank will not rub the ID on internal and OD on external. You need to check the thread mill is size correctly for the threads you are cutting. If you are doing a harder material and want to make a semi rough cut you can use the same tool and call out a thread milling cycle out before the finish thread milling cycle using the same tool. Use a smaller major diameter for an internal thread and and a larger minor diameter for external.

[Muzzer]

If you do it in Fusion, you can specify the stepdown, as with any milling operation. There is a nice canned cycle specifically for threading turning but no equivalent in milling - unless there was a canned cycle for milling threading as such, it wouldn't make any sense.

Here's an example of the final pass of a milling threading operation. I actually used a small boring bar with an internal threading insert as a tool. Unless you manage to trash the bar itself, it's perhaps cheaper than a dedicated thread mill. It's what I had to hand. However, if you are prepared to wait a few weeks, there are some pretty decent carbide thread mills available from AliExpress at a reasonable cost.